An image forming apparatus includes a fixing device for thermally fixing an image onto a sheet. The fixing device includes a heat roller and a pressure roller. At the first printing time, the image forming apparatus prints an image on a sheet for the first time after the image forming apparatus received a print instruction. At the first printing time, insufficient image fixing may occur because the pressure roller in the cold state draws heat from the heat roller and the surface temperature of the heat roller becomes extremely low.
Japanese Patent Application Publication No. Hei 8-241011 discloses a technique for restraining such an insufficient image fixing by forcibly lighting up a heater before a sheet reaches the fixing device for the first time after the image forming apparatus received a print instruction.